Update: added CACHES to settings.py.

Cache settings now default to django.core.backends.filebased.FileBasedCache
with location set to /tmp/django_cache
Update: ATOM feed generator refactored.

* Bugfix: use of request.META["REQUEST_URI"] produces an error in
  development so it is replaced with request.path.

* Bugfix: private articles are now disincluded from the ATOM feed.

* Added uri_prefix to public template context via helpers.ContextHelpers
  so we'll always know the "http://server_name[:port]" address of
  the website. Hopefully, it also works with HTTPS but I have no
  way of testing.